<?php
# add to themeheader() and themefooter() globals
$Blocks

# replace
blocks_visible('l/r');
# with
$Blocks->l;
$Blocks->r;

# replace
hideblock('N');
# with
$Blocks->hideblock('N');

# replace
blocks('left/right/center/down')
# with
$Blocks->display('l');
$Blocks->display('r');
$Blocks->display('c');
$Blocks->display('d');

/*
Make sure your theme/templates/block.html works properly since it will be now finally used by $Block->preview() in admin -> blocks and wherever a developer wants to display a preview of a block.
*/

# header.html, footer.html and blocks.html add minus/plus image file extension like
src="{leftblock.S_IMAGE}.gif"

/*
Only if your module use MEMBER_BLOCK or you as developer want to add a user custom "tools" block like Your_Account and Coppermine does. 
*/
$block = array(
  'bid' = 10000,
  'view' = 1, # 0 all, 1 user, 2 admin, 3 admins, >3 bbgroups
  'side' => 'l', # l, r, c, d
  'title' => _MULTILANG_ALLOWED,
  'content' => 'a string or a callback function()'
);
$Blocks->custom($block);
# just free up some memory
$block = NULL;